score:2
Boost indeed uses the Telstra 3G and 4G network. However, Boost does not have access to the faster Telstra 4GX (700 MHz) network.
You can use the coverage maps provided by Boost and Telstra to compare coverage.
You will notice from these maps that even though the Telstra network is regarded as the best in Australia, there are still very significant areas where there is no coverage at all for your itinerary. You should consider bringing additional communications equipment (such as a EPIRB or a satellite phone) in case you become stranded in a remote area without mobile phone coverage.